Tracy Punshon, Ph.D.

Background: Doctoral and post-doctoral work in Liverpool, UK: Ph.D. on heavy metal tolerance in fast growing trees, post-doctoral work investigating soil amendments for preventing arsenic and cadmium uptake by plants. Post-doctoral work at the University of Georgia's Savannah River Ecology Laboratory (Aiken, SC) on phytoremediation and plant uptake of arsenic from coal combustion by-products.

Areas of Expertise: Elemental analysis and imaging of biological specimens, arsenic in the environment, human exposure to arsenic via diet

Experience: Dr. Punshon joined the Superfund Research Program (SRP) at Dartmouth as a trainee in 2005. She worked as a post-doctoral fellow in the laboratory of Dr. Mary Lou Guerinot, using elemental imaging (SXRF microtomography) to visually confirm the function of a critical vacuolar iron transporter in seeds of the model plant Arabidopsis thaliana. This was a novel application of SXRF at the time, and led to the increased use of the technique in plant molecular genetics. Tracy introduced the Dartmouth SRP group to the studies on arsenic uptake by rice, which led to the study of health effects of dietary arsenic exposure on pregnant women in New Hampshire.

Current: Dr. Punshon joined the Trace Element Analysis Core in 2015, where she conducts elemental mapping collaboratively with researchers within the Superfund Research Program and beyond. Her goal within the TEA Core is to increase accessibility of elemental mapping techniques program-wide, to benefit both the quality of the scientific findings and to foster technological advancements in spatial techniques. Dr. Punshon uses elemental imaging in her own research to understand the transport of contaminants and nutrients across the human placenta at the Center for Molecular Epidemiology at Dartmouth. By combining exposure epidemiology, elemental imaging and immunohistochemistry she hopes to provide mechanistic information about transplacental transport  a much-understudied human organ that influences health both in infancy and in later life. She also works on dietary arsenic exposure to infants and young children as part of the Children's Environmental Health and Disease Prevention Program.

Research: The common theme running through Dr. Punshon's research is understanding the transport and chemical speciation of trace elements in biological systems, in particular the role that membrane integral transport proteins play in a variety of cellular processes that directly influence the environment, such as uptake by crop plants and human exposure. Her early studies focused on nutrient and contaminant metal uptake in plants, with particular attention to distribution and localization of metals. The scope of Dr. Punshon's research has expanded to include human health and exposure epidemiology. Her expertise in the elemental mapping of biological specimens reveals the mode of action of potentially toxic elements, or the functions of genes involved in elemental transport, by showing where and at what amount elements accumulate. Using synchrotron X-ray fluorescence mapping and tomography (SXRF) interchangeably with laser ablation inductively coupled plasma mass spectroscopy (LA-ICP-MS), Dr. Punshon can apply these techniques to a wide range of specimen types.